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HELP! PO420 code

10-09-2005, 08:14 PM
My Fiance has a 99 civic w/ 93k.

About three months ago it started running wierd and to make a long story short it needed a tune up, new plugs and wires and she ran like new.

Less than a day later the CEL came on but it still ran good. FYE the car has NEVER had the CEL come on.

I had the code pulled and it is the P0420-" catalyst efficiency below threshold bank 1" code.

Her dad took it to his mechanic, (not the one I took it to) and they said it need a new Cat.

This didn't sound right to me since the car has low miles (93K) and the CEL just came on after my mechanic started probing around. Her dad is ready and willing to buy a new cat but I think it's something else like a sensor.

Any Ideas woud be greatly appreciated

10-10-2005, 03:14 AM
reset the cel by disconnecting battery. hook it back up. if it comes back on then you need a new cat.

10-10-2005, 02:15 PM
already did that twice and had the code cleared three times at auto zone.

I really don't think the cat is fried at 93k do you?don't they normally last at least 150k or more?
why is this happening right afer a tune up?
I really don't get it!!

she drives easy and burns good gas and maintains it meticulously.

this doesn't make sense.

i may replace the first o2 senser, i heard that may be the problem.

10-10-2005, 04:02 PM
civics have problems with their cat all the time. youll find them all over the forums. check to see if honda had a recall on them or maybe your warranty covers it.

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